1. Field of the Disclosure
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device having light scattering patterns at an edge region of a light guide plate, capable of preventing a hot spot phenomenon from occurring when an edge-type backlight unit is implemented by using light emitting means such as light emitting diodes (LED).
2. Description of the Background Art
Generally, an LCD device is a representative flat display device for displaying images by controlling an optical transmittance so as to correspond to image signals. However, since the LCD device is not a spontaneous light emitting device, an additional light source that provides light from a rear surface of a liquid crystal (LC) screen is required to display images.
The light source that irradiates light from a rear surface of a liquid crystal module (LCM) to a front surface is called as a backlight unit. The backlight unit includes a lamp, and integrated components for a power circuit to drive the lamp and for uniformly planarized light. The backlight unit may be largely classified into a direct type and an edge type according to a method for irradiating light. Recently, direct type and edge type of flat backlight units adopting a planar light source such as light emitting diodes (LED) are being actively researched.
Here, in the edge type backlight unit, a light source is disposed at a side surface of an LCD module, and light emitted from the light source forms planarized light through a light guide plate. Since the edge type backlight unit has a low brightness, a light guide system applied from the light source to a comparatively far distance has been required to obtain a uniform brightness. In order to minimize a loss in transmitting light to the comparatively far distance from the light source, advanced optical techniques have been demanded.
Hereinafter, the edge-type LED backlight unit will be explained with reference to the attached drawings.
FIG. 1 is an exploded perspective view showing an edge-type light emitting diode (LED) backlight unit in accordance with the conventional art, and FIG. 2 is a view showing a distributed state of light through simulation of a liquid crystal display (LCD) device of FIG. 1.
As shown in FIG. 1, the edge-type LED backlight unit comprises a light source 10 for providing light, a light guide plate 32 for guiding light provided from the light source 10, and a diffusion sheet 34 and a prism sheet 55 for enhancing an optical characteristic of light having passed through the light guide plate 32.
Here, the light source 10 is composed of a substrate 12 and a plurality of LEDs 14. The LEDs 14 are mounted on the substrate 12 in one row, and are electrically connected to an external power source. The substrate 12 having the plurality of LEDs 14 mounted thereon is insertion-fixed into a light source cover 16. A coupling groove 16a is formed at an inner surface of the light source cover 16 along a long axis direction of the light source cover 16. Accordingly, the substrate 12 is insertion-fixed into the coupling groove 16a. 
The light guide plate 32 guides light provided from the LEDs 14 of the light source 10, thereby distributing light onto an entire part of an upper surface of the light guide plate 32. Here, a reflection plate 30 disposed below the light guide plate 32 serves to enhance a reflection efficiency of light.
The diffusion sheet 34 is disposed on an upper surface of the light guide plate 32, thereby uniformly distributing light having passed through the light guide plate 32.
The prism sheet 55 composed of first and second prism sheets 52 and 54 is disposed on an upper surface of the diffusion sheet 34. The prism sheet 55 serves to introduce light provided from the diffusion sheet 34 to an image region, that is, a constant region of an LC panel (not shown) that displays images.
A protection sheet 56 for protecting the prism sheet 55 from an external scratch may be disposed on the upper surface of the prism sheet 55.
The LCD device having the LED backlight unit requires a planar light source so as to display images on a screen. Light emitted from an LED packet 14 in the form of points is converted into a planar light source after passing through the light guide plate 32.
In order to reduce a loss of light provided to the LED package 14 from the light guide plate 32, a spacing distance between the LED package 14 and the light guide plate 32 has to be minimized. Here, an emission width of the LED package 14 is predetermined from its structure, and a degree of light concentration becomes weaker towards the side portions as compared to the middle portion of the LED package 14.
As a result, the light guide plate 32 (or LC panel) having the LED package 14 arranged thereon receives, from the LED package 14, relatively weak light at an edge region thereof. This may cause a specific part, ‘A’ to be displayed as a dark area with a semi-circular shape.
The dark area degrades appearance quality of the screen, thereby lowering the reliability of the product.